This invention relates to a display device for displaying an image or the like by use of electrostatic force.
At present, a large-scale image display device has received much attention. FIG. 1 shows various types of conventional large-scale display devices for comparison. In FIG. 1, the expandability indicates whether or not a large screen can be easily formed by combining small displays.
Next, individual displays are explained. A CRT (Cathode Ray Tube) is a most widely used display device, but it is technically difficult to form a thin type and large display device of 40 inches or more. Further, since a large display device becomes relatively heavy, it becomes difficult to handle. Further, there is provided a display technique for combining small CRTs, but it is difficult to completely eliminate the boundary lines.
A PDP (Plasma Display Panel) has received much attention as a thin type display of 40-inch size, but it has problems that the maximum luminance thereof is lower than that of the CRT, the power consumption is large and the manufacturing cost is high and hard to be even 70 U.S. dollars for one inch. Further, when a display of larger size is formed, the manufacturing cost will be at least doubled. This is because the manufacturing line is constructed in accordance with the display size which will become most popularized. When a display of 40 inches or more is formed by combining small displays, the boundary lines become noticeable since the PDP is of a low-pressure gas-filed type and the peripheral wall cannot be made small.
A PALC (Plasma Addressing Liquid Crystal) is a combination of a liquid crystal cell and plasma generation electrodes. That is, a plasma generation cell is formed separately from the liquid crystal cell and the two cells are stacked together. The plasma cell has a function of selecting one or some of the pixels in the liquid crystal cell to which the potential is applied. It is said that the display of a large area can be attained at a low cost in comparison with the selecting system using the conventional TFTs (Thin Film Transistors). However, in this type of display, since the manufacturing line is constructed in accordance with a specified size (for example, 40 inches) as in the case of PDP, the manufacturing cost is abruptly raised if the display size is increased. Further, like the PDP, the boundary lines become noticeable when it is formed by combining small displays.
In the case of LCD (Liquid Crystal Display), the maximum size thereof is 20 inches at present and is 30 inches even if the combination technique is used. Further, the manufacturing cost will be made high if it is made large since TFTs are used.
An FED (Field Emission Display) is a system in which fine cold cathodes for emitting electrons are arranged on a silicon substrate or glass substrate and electrons emitted from the cold cathodes are applied to a fluorescent material for display. It is said that the maximum luminance which is almost equal to that of the CRT can be attained in this system, but it is difficult to uniformly form the cold cathodes on the large substrate and it is difficult to form a large screen display.
An LED (Light Emitting Diode) display is a large display formed by arranging a large number of light emitting diodes. It is most widely used as a large and thin type display of 40 inches or more. However, the power consumption is large and the manufacturing cost is high. Further, since the light emitting diodes are used, the maximum luminance is not so high.
That is, in the conventional large and thin type display, a display which has high expandability and which can be formed at a low cost is not present.
Further, a movable film type display device in which an electric field is applied to a conductive plastic foil or metal foil to move the same as a shutter for display is provided (Jpn. Pat. Appln. KOKAI Publication No. 1-72195, Jpn. Pat. Appln. KOKAI Publication No. 1-72196, Jpn. Pat. Appln. KOKAI Publication No. 1-108598 and Jpn. Pat. Appln. KOKAI Publication No. 4-12391).
In the above display device, a light source such as an LED or electric lamp is inserted into a cylinder whose surface is coated with a transparent electrode and a conductive movable film is set to cover and conceal the cylinder. Then, a potential difference is applied between the cylinder and the movable film to displace the movable film so as to change the amount of light emitted from the cylinder.
It is considered that a thin type display device of low cost can be formed by use of the above display method. However, a concrete method for constructing a large display by use of the movable film type display device has not been provided.